Wireless data networks serve wireless user devices with mobile data communication services like internet access, voice calling, and video calling. The wireless data networks have wireless access points that exchange data over the air with wireless user devices. In Long Term Evolution (LTE) networks, the wireless user devices are referred to as User Equipment (UE), and the wireless access points are referred to as evolved NodeBs (eNodeBs). The UEs exchange data over the air with the eNodeBs at specific times and frequencies that are known as resource blocks.
LTE eNodeBs use Carrier Aggregation (CA) to serve more bandwidth to the UEs. For CA, an eNodeB schedules and transmits data to a single UE over multiple simultaneous resource blocks—multiple frequency bands at the same time. Thus, CA is a high-bandwidth communication service having a fast data rate. The resource blocks that are transmitted from the eNodeB to the UE form a downlink that comprises a Primary Component Carrier (PCC) and additional Secondary Component Carriers. The resource blocks that are transmitted from the UE to the eNodeB are not simultaneous and form an uplink that comprises only a single carrier.
The LTE eNodeBs use an error correction technology known as Hybrid Acknowledgement Repeat Request (HARQ). With HARQ, the eNodeB transfers data to a UE, and the UE transfers acknowledgements for received data to the eNodeB. The eNodeB re-transmits the data if the UE does not acknowledge the data receipt. When HARQ is used with CA, the downlink data is transmitted over the PCC and the additional SCCs, but the data acknowledgements all share the single uplink PCC. Although CA boosts wireless downlink speeds, CA also consumes more uplink resource blocks.
LTE eNodeBs use Multi-User Multiple Input Multiple Output (MIMO) to transfer data to multiple UEs over shared resource blocks. The eNodeB and a pair of the UEs use beamforming and timing technology to maintain data separation in the shared resource block. Since the two UEs share the same resource block on the downlink, MU-MIMO is a low-bandwidth service that efficiently uses network resource blocks and serves low-bandwidth UEs in a more cost-effective manner. Due to the use of beamforming technology on the downlink, the UE transfers Sounding Reference Signals (SRS) on the uplink to the eNodeB. The eNodeBs process the SRS to determine the radio channel response between the eNodeBs and the UEs. The eNodeBs beamform the downlink signals based on the uplink channel response. Although MU-MIMO is an efficient use of bandwidth, MU-MIMO requires uplink resource blocks for the beamforming SRS.
When CA usage spikes, the spike in CA SCCs increases the number of uplink resource blocks for the spike HARQ acknowledgements. When MU-MIMO usage spikes, the spike in SRS increases the demand for uplink resource blocks. At some point of uplink congestion, the SRS does not get the resource blocks to reach the eNodeBs and the beamforming quality of the MU-MIMO service suffers. In addition, the uplink congestion inhibits the resource blocks that transport the HARQ acknowledgements to the eNodeBs which causes unnecessary data re-transmissions and the CA service suffers.